(1) Field of the Invention
The invention relates to heating ventilation and air conditioning (HVAC) systems. More particularly, the invention relates to fans for such systems.
(2) Description of the Related Art
Fans are ubiquitous in HVAC systems. Many fan configurations exist. A typical electric fan includes a motor having a shaft protruding from one end. A fan assembly is mounted to the shaft so as to be driven by the motor. One group of fan assembly configurations involves molding a plastic component over a metallic hub insert. The plastic component includes a hub surrounding the insert and blades radiating outward from the hub. The plastic component may further include a shroud at outboard ends of the blades. In such configurations, the use of plastic generally provides lightness and ease of manufacturing and the use of a metallic insert provides a robust precise connection to the motor shaft. The engineering of the insert and its interface with the plastic component presents a number of considerations. The insert may, advantageously, be light. The insert requires an appropriate robust interface with the plastic component to reliably transmit torque and thrust. Various forms of fluting and other complex surface configurations have been proposed to achieve advantageous performance.